Funds are requested for the partial cost of purchasing a high-resolution, multinuclear Bruker Avarice 21.44 Tesla (900 MHz 1 H frequency) NMR spectrometer which will become part of National Magnetic Resonance Facility at Madison (NMRFAM), Biochemistry Dept., University of Wisconsin-Madison. Some matching funds are already in hand from the NIH NCRR BRTP and the University of Wisconsin- Madison. A grant from the NSF MRI program is pending. NMRFAM is a shared instrumentation facility used by researchers at the University of I Wisconsin-Madison campus and by visitors from other research institutions in the United States and abroad. NMRFAM's new facility, which houses five NMR systems operating at 400 MHz, 500 MHz (two systems), 600 MHz, and 750 MHz, was designed to handle the special siting requirements of additional NMR systems operating as high as 1.2 GHz. Research time on the 900 MHz NMR spectrometer will be allocated to competing projects on the basis of scientific merit. The local and external advisory committees to NMRFAM will oversee its use. The support staff at NMRFAM includes seven Ph.D. scientists, a computer programmer, a postdoctoral research associate, and an administrative specialist who handles scheduling and communications with users. NMRFAM has a proven track record for making new technology available to its users and for keeping instrumentation in top operating condition. The user base at NMRFAM includes graduate students, postdoctoral research associates, staff scientists, and principal investigators from 68 laboratories (43 within the University and 25 external). The 900 MHz spectrometer will be devoted to experiments that require its uniquely-high field strength: TROSY studies of larger proteins, investigations of field-dependent molecular ordering effects, studies of the field dependence of chemical exchange and relaxation phenomena, and functional studies of proteins and other biomolecules that require exceptional resolution and/or sensitivity.